Green printing materials for cosmetic plastic packaging

Green printing materials for cosmetic plastic packaging

I. Introduction

With the deterioration of the global environment, people are increasingly aware of the importance and urgency of sustainable development, and phenomena that are detrimental to the ecological environment and human health should be highly valued and strictly restricted. The excessive consumption of natural resources and energy in printing production and the pollution of the natural environment caused by packaging waste have become a bottleneck in the rapid development of the printing industry, especially in cosmetic plastic packaging printing. This requires us to change our production philosophy. Only by changing to a green and environmentally friendly printing method as soon as possible can we conform to the trend of developing a harmonious society.

At present, green printing is leading the development of the global printing industry with its strong influence. Abroad, European environmental regulations have clearly limited the emission of volatile organic compounds in the printing industry, which not only increases the content of waste disposal, but also provides ways to reduce ink loss. According to statistics, 60% of printed matter in the UK is printed with alcohol-free or low-alcohol inks. The U.S. Environmental Protection Agency strongly opposes the use of solvent-based inks. Flexo ink is currently the only non-toxic ink approved by the American Food and Drug Association and is widely used in packaging and printing of food and drugs. In addition, in developed countries such as Europe, the United States, and Japan, ink is gradually replacing traditional solvent-based inks in addition to offset printing.

2. Green plastic packaging materials

Green plastic packaging refers to an environmentally friendly degradable plastic packaging developed from natural plants and related minerals that is harmless to the ecological environment and human health, is conducive to recycling, is easy to degrade, and is sustainable. Its most important The meaning is to protect the environment and also have the meaning of resource regeneration.

There are currently many degradable packaging plastics, and the ones that have made good progress and applications include photodegradable plastics, biodegradable plastics, and photo/biodegradable plastics. In the chemical structure of degradable materials, new polymer synthesis technology introduces easily decomposable groups, easily broken chemical bonds, and easily transferred atoms or groups. Only under such structural conditions, molecules can break the molecular chain under the action of light and microorganisms, destroy the structure, and then quickly decompose in nature, without polluting the environment, and can be recycled and reused, which embodies this material advantages and value. Secondly, it is light in weight, easy to process, good in packaging performance, and easy to surface decoration.

3. Degradation principles and applications of various materials

1. Photodegradable plastics

Photodegradable plastics include synthetic and additive types, but the two degradation principles and processes are the same. Because photodegradable plastics add specific photosensitizers to ordinary or modified plastics, this type of photosensitizer can effectively absorb ultraviolet rays in sunlight under natural light, obtain energy and become excited, and then transfer the energy to or Transfer to easily excited groups or chemical bonds to perform photochemical reactions, which leads to the degradation of macromolecules and the continuous formation of small molecule fragments that are easily swallowed by microorganisms. The purpose of degradation is achieved. If an autooxidizing agent is added to the material at the same time, it will react with metal salts in the soil to generate peroxides. These peroxides will then act on the carbon chain skeleton to break the molecular chains and degrade them into small molecular compounds that are easily eaten by microorganisms. .

Since photodegradable plastics can only be degraded under sunlight irradiation conditions, they are highly restricted by geographical environment and climatic conditions. It is difficult to achieve accurate time control and the buried part cannot be degraded. Therefore, large-scale promotion and application have been limited. limits.

2. Biodegradable plastics

Biodegradable plastics refer to plastics that can be degraded by microorganisms. According to their production technology, they can be divided into: microbial synthesis type, synthetic polymer type and blending type. Due to the special factors of the internal structure and composition of the material, when this kind of packaging plastic is discarded, it can gradually and completely decompose into small molecular compounds under the action of various bacteria, enzymes, microorganisms, etc. in the natural environment, and finally decompose into water and carbon dioxide. and other inorganic substances. Biodegradable plastics have good biocompatibility and biodegradability and are widely used in packaging materials and pharmaceutical fields.

The most researched in our country is the incomplete biodegradable type mixed with starch and polyolefin plastic. The degradation mechanism of this type of plastic is that the starch granules are first invaded and consumed by fungi and bacteria, thereby weakening the strength of the plastic. At the same time, through contact between the plastic and certain salts present in the soil, peroxide is formed through auto-oxidation, which promotes the plastic to degrade. The molecular chains of the polymer in the plastic are broken, and they promote each other and complement each other. The bacteria consume the starch, which increases the surface area of the plastic and is conducive to autoxidative degradation. Over and over again, the polymer chains gradually break and shorten, reducing the strength of the plastic until the molecular weight of the polymer is reduced to a level that can be metabolized by microorganisms.

3. Photo/biodegradable plastics

Photo/biodegradable plastics are plastics that have synergistic degradation effects under the dual effects of light and biology. The key to the dual-degradability of this plastic is that two inducers are added to its overall material, that is, the material is mixed with biodegradable starch, a controllable photodegradable photosensitizer that can induce chemical reactions, or Compounded with photosensitizer and auto-oxidant and other degradation aids. Among them, the photosensitizer with controllable photodegradation does not degrade the plastic before the specified induction period, and has an ideal controllable decomposition curve. During the induction period, the mechanical properties remain above 80%. After reaching the use period, the mechanical properties decline rapidly. Moreover, it can also decompose the plastic into fragments regularly by adjusting the concentration ratio between them. Then, under the combined action of automation agents and microorganisms on starch, this material will be quickly decomposed. This kind of plastic is non-toxic, harmless, easily degradable and recyclable. 4. Green printing of plastic packaging.